Photography



Patented Apr. 1940 UNITED STATES I PATENT- OFFICE,

2,190,133 rnoroamrmr India Nb Drawing. Application September 21, 1937,

Serial No. 164,990. ber as. 1936 v 9 Claims.

tography, particularly color photography, and has for its principal object to provide a relatively simple process'whereby superimposed silveK images in multi-layer photographic material (film or plate) may be isolated in such a form that they can be employed as separation negatives. By the attainment of this object, it becomes possible, in particular, to produce colored prints on paper. from a multi-layer film exposed, with a single exposure, in an ordinary camera. According to invention, an image in a multi-layer material isolated by transferring it from the material to a metal plate in the form ofa metallic deposit. Forthe production of sepa-' ration negatives, one or more images in'a multilayer (multi-color) material is or are transferred separately to metal and thencefto a transparent support or supports.

- For this purpose, use is advantageouslymade ence of a deposition agent, that is a partial sol vent for the halide'in thepresence of which the said halide is reduced by the metal of the plate. By this means, a silver deposit corresponding to the image is obtainedupon-the plate.

In order to transfer this deposit to a transpar-' ent support, firstly its adherence to the plate may be loosened as hereinafter set forth, by making the plate the anode of an electrolytic cell, and

then the support may be applied to the plate un-- der such conditions that the deposit remains ad hering tov the support when-the latter is removed. Although the invention may be applied to any multi-layer film of the nature referred to above.

In Great Britain Septem- This invention relates'tolmpr'ovements in phois made of a multi-layer tri-colour film of the.

type known by the trade-mark Kodachrome.

Such a film may comprise the following series of layers of gelatin'e: A first or uppermost active layer sensitive to blue, a thin inactive layer, a secand active layer sensitive to green, a further thin example, Celluloid. As far as the present example is concerned, it may be assumed that this film has been exposed, developed and fixed by ordinary methods. Thefilm then contains. three developed negatives, one in each of the three active layers.

Ta facilitate later steps of the process, if the gelatine is not already sufliclently hard, the whole film may firstly be hardened to a definite extent, for example by immersing it for 15-20 minutes in a 5% solution of alum. It is then carefully dried.

The next step consists in bleachingthe first active layer only, i. e., converting. the silverof the image in that layer into silver halide. For this purpose, it is advantageous to use a. bleaching agent, such as a strong solution of ferric chloride or a "loaded bleacher, which penetrates gelatine relatively slowly but effects the bleaching relatively rapidly. The time required ,to bleach the first layer by this'means depends upon thehardness of the gelatine and the strength of the solution used. When the predetermined time has elapsed, the

film is immersed in a stop-bath to arrest the bleaching, for instance a weak solution of sodium carbonate.

After the film has been rinsed, it is immersed in a deposition agent. Several such agentsare' referred to in our aforesaid specification. In the present example, it is preferred to immerse the film for about 30 seconds in a 20% aqueoussolution of sodium chloride. Other preferred agents 40 it. has provedv advantageous to employ a special are potassium chloride and sodium sulphite. Hy-

: film in which two of the active layers are separated not by the usual gelatine layer' but by a weak adhesive such as glue or 'gum or by a wa-. ter-proof varnish or wherein two active layers I are separated by weak adhesive or a low-melting plate for, say, 7-10 minutes. The silver chloride f' in the said first layer is converted into'metallic gelatine and two active layers by. water-proof I varnish or ahigher-melting gelatine respectively. silver which adheres to the copper plate in the In some cases also,'it is advantageous to employ a film in which the front active layer is attached at the front to an additional transparent supporting layer.

Various-manners of carrying the invention into eflect will. now be more fully described by way of example: l a

Forafirst example, it will be assumed that use drochloric acid is not recommended and ammonium hydroxide and ammonium sulpho-cyanide are notsuitable. The film is then pressed with its first active layer in contact with a clean copper anode of an electrolytic cell of which the oath.

ode is a plain copper plate, the plates being preferably disposed horizontally. Various electrolytes which do not attack-silver may be -employed, but

'mentarily in water.

in this example use is made of a copper salt solution, for instance a copper sulphate solution containing a small quantity of sulphuric acid or a plain'soluti n of sulphuric acid. Upon the passage of a current through the cell, for insance .6 ampere with an E. M. F. of 2 volts. it is found that the copper under the silver deposit is dissolved with the effect that the adherence of the silver is loosened. The plate is rinsed after removal from the cell.

The loosened silver deposit is now transferred to a transparent support, such as asheet of Celluloid, which has been coated with a film of dry hardened gelatine. The plate has weak hydrochloric acid poured over it and is then dipped mo- The transparent support, which may first be moistened, is laid with its gelatine film in contact with the slightly acid moist surface of the plate and light pressure is applied.

- In the short period for which the gelatine becomes tacky,". the silver deposit adheres strongly- Now, while the above treatment of the silver deposit is being prosecuted, the film is available, after removal from the water, for the" commencement of the second stage of the process. Before the second active layer of the film isdealt with, it is desirable to remove the layer of gelatine from which the deposition of the silver on the copper plate was efiected in the first stage. This removal can be performed by the exercise of gentle friction upon the surface of the first layer of gelatine until a fracture is induced between it and the second layer, whereafter the first layer can be readily removed. The friction may be exerted by means of a small swath of cotton wool which may also be used to effect the removal of the gelatine; The intermediate inactive layer of gelatine may accompany the said first layer, but, owing to its thinness, it is not important if this, does not occur. The film is then dried.

The procedure adopted in the first stage is repeated for the second active layer, commencing with its bleaching and terminating with the production of a SBCOIBCI separation negative. 1

The procedure may then berepeated for the third layer in order to produce the third separation negative. However, the removal of the layer of gelatine from which the silver was depositedn in the second stage actually leaves a third negative, on the original support, of the kind required.

From the set" of tri-color separation negatives produced, color-prints on paper can be obtained by any of the known processes.

Various departures from the. above-described example can be made. For instancafor some purposes, it may be convenient to commence by reversing the images in the multi-layer film.

Furthermore, where the steps of the. procedure have a counterpart in my above-mentioned application, alternatives described in the latter may be utilized in carrying steps of the present invention into effect. -For instance, the electrolytic step may be replaced by treatment, described in the aforesaid application, whereby the silver de- This adhesive should-be colorless and tra'nspar-' ant and may or may not be water soluble. The fifth layer is a layer'of inactive -ge1atine, and connects the fourth layer to the sixth layer which is an active layer sensitive to red. The seventh or rearmost layer is the usual supporting layer of Celluloid.

After exposure, but before development, the film is placed in water or other appropriate solvent for the adhesive used. The blue-sensitive layer carried by the first or Celluloid layer then becomes detached from the other layers and can be developed and fixed for the production of a first separationnegative. Next the rest of the film is also developed and fixed. and the silver image in the green-sensitive layer is extracted and transferred to a transparent carrier by the process described in the first example. The redsensitive layer is left on the rearmost supporting layer. It will be noted that this process calls for the extraction ofonly one silver-image and does not necessitate the removal of a layer of gelatine.

Alternatively the film employed may comprise the following layers: Blue-sensitive layer," layer of transparent and colorless waterproof varnish, green-sensitive layer, gelatine layer, red-sensitive layer, Celluloid layer.- n developing and fixing such a film, a negative image will be produced in the first layer only. This image is transferred to a transparent carrier as in the first example. The film is then immersed in acid. e. g., hydrochloric acid, or alkali, e. g., sodium hydroxide, and the gelatine of the first layer is removed by rubbing and washing. The exposed layer of varnish is next removed by immersing the film in a solvent for the varnish. On redeveloping and fixing the film,,negative images will beproduced in the two remaining sensitised layera.

The green-sensitive layer is transferred to a transparent carrier as in the first example.

layer is a layer of' inactive layers, between, the blue and green low-melting gelatine acts like a weak adhesive and the blue-sensitive layer or the front supporting layer may be separated from the other layers, without separating or dissolving the green 7 metal plate in the presence of a partial sblvent and red sensitive layers. by immersing the film in water at an intermediate temperature, say 105 1". In the second case,-dissolving the lowmelti ng gelatine in water at the intermediate temperature allows of the easy removal of the gelatine left b'ythe extraction of the image in the blue-sensitive layer in accordance with the first example.

' I claim:

1. Process for the separation of superimposed images in multi-layer photographic mm terial for the production of separation negatives for color printing, comprising the steps of isolating an image from the said material by transferring it therefrom, in the form of a metallic deposit, to a metal surface and thereafter removing the said metallic deposit from the said surface onto another support.

2. Process for the production of a separation negative from a. multi-layer photographic material, particularly multi-color photographic material, comprising isolating and transferring an image as a metallic deposit from a layer of the said material to a metal surface and transferring the said deposit thence to a transparentsupp rt. v

3. Process for the isolation of an image in a multi-layer photographic material in a layer of which the image to be isolated is. defined in a halide of silver, comprising the steps of applying the surfaceof the said layer in contact with a smooth metal plate in the presence of a partial solvent for the halide in whose presence the said halide is reduced by the metal of the plate, whereby a metallic silver deposit is produced upon the said plate, and thereafter removing the said metallic deposit from the said plate onto another support.

4. Process for the isolation of an image in a multi-layer photographic material in a layer of which the image to be isolated is defined in a halide of silver, comprising applying the surface of the said layer in contact with a smooth metal plate in the presence of a partial solvent for the halide in whose presence the said halide is reduced by the metal of the plate, whereby a me-' tallic silverdeposit is produced thereon, and sub-' sequently loosening the said deposit as a whole from the plate by making the latter the anode of an electrolytic'cell and passing a current through the cell.

5-. Process for the isolation of an image in a multi-layer photographic material in a layer of which the image to be isolated is defined in a halide. of silver,;comprising applying the surface of the said layer in, contact with a smooth for the halide in whose presence the said halide,

is reduced by the metal of the plate and appears as a metallic silver deposit thereon, loosening the adherence to the said deposit to the metal plate and transferring the said deposit to a transparent support to whose surface the deposit has a greater adherence than to the plate, for example Celluloid coated with moistened gelatine, by placing the said surface in contact with the surface posit.

6. Process for the separation of images in a multi layer photographic material in which the images are contained in layers of gelatine, comprising extracting an image fromthe said material in the form of a metallic deposit, and removing the layer of gelatine left behind by the extraction of the said deposit before treating underlying layers of the material.

'7. Process for theseparation of images in a photographic material comprising front and rear supporting layers-andthree superimposed active layers of which two are connected by a more readily soluble agent then the others, comprising sep? arating the material into two parts, each with its supporting layer, by dissolving the readily soluble agent, and isolating the image from the upper active layer, in the part containing two such layers, by transferring the said image in the form of a metallic deposit to a metal surace. 1

8. Process for the separation of images in a photographic material comprising several superimposed active layers whereof two are separated by a layer of water-proof varnish, comprising the steps of developing the active layer above the layer of varnish, isolating the image in that active layer by transferring it as a metallic'deposit to a metal surface, dissolving and removing the of the metal plate bearing the devarnishlayer, and developing the active layer exposed by such removal of the varnish layer. 9. Processfor the separation of images in a photographic material comprising three superimposed active layers whereof two are connected 'by a layer of low-melting gelatin; and two by a layer of higher-melting gelatine; comprising the steps of isolating the image in the active layerabove the layer of low-melting gelatine by transferring it as a metallic deposit to a metal surface, and removing the vacated gelatine of that active layer by dissolving the layer of lowmelting gelatine in water at a temperature below the point'at which the higher-melting gelatine would be dissolved.

KEVIN WILLIAM CA'I'ON WEBB. 

